This project will evaluate the proportions and distributions of lymphocyte subpopulations in human gingiva from sites displaying recent attachment loss versus periodontal stability. Small interproximal gingival biopsies will be obtained from three sites in each of 30 patients: 1) site demonstrating at least 2 mm clinical attachment loss during the previous 3 months; 2) similar site which has shown no recent attachment loss; and 3) healthy site with minimal pocket depth. Serial frozen sections will be prepared and commercially available monoclonal antibodies used to identify surface markers on T, T helper/inducer, T suppressor/cytotoxic, B, and on activated (IL 2 receptor) T and B lymphocytes. Cells will be labeled using an avidin-biotin-peroxidase (ABC) system. Double-labeling experiments will identify subpopulation and activation markers present on the same lymphocyte. Peripheral blood lymphocytes from each patient will also be tested with the above antibodies (fluorescent labels) for comparison. Description of lymphocyte subtypes, activation, and their distribution relative to an active periodontal pocket is important information in assessing the role of the immune response in periodontal attachment loss. In addition, unique immunologic characteristics may become evident and may be used to identify the active periodontal lesion. Long-term objectives include combining the above technology with identification of purified bacterial antigens in tissue using monoclonal or monospecific antibodies. This would allow for comparative mapping to identify specific antigen/lymphocyte interactions in situ in various stages of periodontal disease. These histologic probes would be used in the description of the immunopathogenesis of periodontal disease and to identify deagnostic markers of active periodontitis.